Significant serum lipoprotein concentration differences have been reported to occur between patients with mammary carcinoma, normal indivivuals with a family history of cancer, and normal individuals without family history of cancer. The objective of this work is to study the chemistry of the serum lipoproteins of individuals in these three groups. The first objective will be to ascertain whether the differences are quantitative only or whether chemically different aproproteins, and consequently lipoproteins, occur. If qualitative differences are found, then the next objective will be to determine the chemical basis of the differences.